I am having the same problem with the same error message as TheCapn. I have checked the serial number both on Xara.com (registered products) and in my confirmation email and they match. The email address is also correct as per my Xara account. I have had no response from Xara support and am running out of trial days!
I have set the program to Run as Administrator and have changed my default browser from Chrome to Internet Explorer as advised by Magix support.
The product is registered with Xara - I just need to activate!
Any other ideas please?